If a company wants to be the anchor tenant for 2 WTC before there is one for 3 WTC, (or doesn't want to be it for 3 WTC but 2 WTC) tower 2 would get built first.

Keep in mind also that Silverstein only has a minimal lease requirement before getting financial assistance from the Port Authority and the City to get tower 3 built. Tower 2 has none of those guarantees, and will likely need to lease more space to get traditional financing before the full tower can be built. It will happen, given time, but New York didn't build a lot of speculative office buildings when things were great. Financing, though not impossible, is still difficult to get.

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“Office buildings are our factories – whether for tech, creative or traditional industries we must continue to grow our modern factories to create new jobs,” said United States Senator Chuck Schumer.